The visual detection technology plays an important role in the industry of precision casting. With pertinence to the features of crack images of precision casting, an automatic detection and identification software for cracks of precision casting integrating crack segmentation, identification, measurements and extractions was designed and developed. Adopting the threshold segmentation, morphological processing, feature identifications as well as feature extraction and proposing a detection method with pertinence to the precision casting crack characteristics. The software effectively eliminates the influences on the detection results by the operators due to such factors as the detection environment, fatigue degree, visual resolution and working experience. The processing of the actually collected crack images of precision casting verified the efficacy and practicality of the software in the field of casting detection.